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J. Bacteriol. doi:10.1128/JB.00207-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Growth of Escherichia coli: Significance of Peptidoglycan Degradation during Elongation and Septation

Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111

^* To whom correspondence should be addressed. Email: tsuyoshi_uehara{at}hms.harvard.edu.

	Abstract

We have found a striking difference between the modes of action of mecillinam and compound A22, both of which inhibit cell elongation. This was made possible by employment of a new method using the E. coli peptidoglycan (PG) recycling mutant, ampD, to analyze PG degradation during cell elongation and septation. Using this method, we have found that A22, which is known to prevent MreB function, strongly inhibited PG synthesis during elongation. In contrast, treatment of elongating cells with mecillinam, which inhibits PBP2, allowed PG glycan synthesis to proceed at a near normal rate with concomitant rapid degradation of the new glycan strands. By treating cells with A22 to inhibit sidewall synthesis, the method could also be applied to study septum synthesis. To our surprise, over 30% of newly synthesized septal PG was degraded during septation. Thus, excess PG sufficient to form at least one additional pole was being synthesized and rapidly degraded during septation. We propose that during cell division rapid removal of the excess PG serves to separate the new poles of the daughter cells. We have also employed the new method to demonstrate that PBP2 and RodA are required for the synthesis of glycan strands during elongation and that the periplasmic amidases that aid in cell separation are minor players cleaving only one-sixth of the PG that is turned over by the lytic transglycosylases.

This article has been cited by other articles:

• Park, J. T., Uehara, T. (2008). How Bacteria Consume Their Own Exoskeletons (Turnover and Recycling of Cell Wall Peptidoglycan). Microbiol. Mol. Biol. Rev. 72: 211-227 [Abstract] [Full Text]